Structural Determination of Polysaccharides Lichenin Using Logically Derived Sequence Tandem Mass Spectrometry

Abstract

A new mass spectrometry method, logically derived sequence (LODES) tandem mass spectrometry (MSn), was applied to determine the primary structure of polysaccharide lichenin. Conventional polysaccharide structural analysis requires complex processes, including derivation, permethylation, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectrometry. Many of these processes can be replaced by LODES/MSn. In this new method, polysaccharides are hydrolyzed into monosaccharides, disaccharides, and oligosaccharides, and structures of these molecules are determined using LODES/MSn. The application of LODES/MSn for determination of primary structure of polysaccharide lichenin was demonstrated. The repeating unit of lichenin was determined to be An-Bn, where A represents β-Glc-(1 → 4)-β-Glc-(1 → 4)-β-Glc-(1 → 3)-Glc, B represents β-Glc-(1 → 4)-β-Glc-(1 → 4)-β-Glc-(1 → 4)-β-Glc-(1 → 3)-Glc, n is an integral, and n ≥ 2 exists but n = 1 cannot be excluded. LODES/MSn, which substantially reduces the time, effort, and sample quantity necessary for structural determination of oligosaccharides, is a powerful tool for polysaccharide primary structural determination.